Propellant explosive



Patented June 4, 1935 UNITED smr zs PATENT OFFICE PROIELLANT EXPLOSIVE Edward Whitworth,

Saltcoats, Scotland, assignor to Imperial Chemical Industries Limited, a corporation of Great Britain No Drawing. Application May '15, 1933, Serial N0. 671,279. In Great Britain May 18, 1932 8 Claims.

This invention relates to the production of propellant explosives of the double base solventless type, i. e., those containing nitrocellulose and nitroglycerlnor the like and in the manufacture of which no volatile solvent is used.

In the manufacture of this type of propellant it is customary to employ a non-volatile sub-- is rather low, with the result that the nitroglycerin present in anumber of widely used propellants is 'lnsufll'cient to dissolve the desired amount of ethyl centralite.-

It is known that symmetrical dimethyl diphenyl urea (methyl centralite) has properties which correspond generally to those of ethyl centralite, but the solubility in nitroglycerin is still lower than thatof ethyl centralite and also the setting point of methyl centralite is higher stituted for ethyl centralite.

than that of ethyl centralite, so that the difficulties in the manufacture of the propellant are still further increased if methyl centralite is sub- We have now found, however; that by employing a mixture of ethyl centralite and methyl centralite the solubility of the mixture in nitroglycerin is considerably greater than that of the single substances, and also that the setting point of the mixture is definitely lower than that of either substance.

.Moreover, the gelatinizing power and stabilizing power of the mixture are of the single substances.

Our invention, therefore, consists in an improved methodfor the manufacture .of gelatinized propellant explosives of the type containing nitrocellulose and nitroglycerin or the likemitric ester, according to which nitrocellulose is gelatinizedwith nitroglycerin or the like nitric ester and a mixturesof ethyl centralite and methyl centralite in the absence of a volatile solvent.

We have also found that there is a eutectic mixture of ethyl centralite and methyl centralite, containing approximately 77 parts by weight of ethyl centralite to 23 parts of methylcentralite, this eutectic mixture having the, lowestsetting Point of I allthe mixtures. The setting points and solubilitiesin, nitroglycerin of ethyl cenat least equal to those tralite, methyl centralite and of the eutectic mixture are given in the following table:

1dfilubilityt in Sew 5 Substance 1 glycerin at point Ethyl centralite I l7 gm. 70 0. Methyl centralite 4. gm. 120 C. Eutectic mixture 50 gm. 61 C. 10

It will therefore be seen that the employment of the mixed centralites in the manufacture of propellant explosives of the typedescribed offers considerable advantages over the use of either centralite by itself. We prefer to use the eutectic mixture, on account of its superior properties to other mixtures-and also because it is easily prepared as a uniform product, but we may also use the mixed centralities in otherproportions. 2 0' The advantages of the use of the mixed centralites become apparent during the actual process of manufacture of solventless propellants. The preliminary operation ofmixing the nitroglycerin, nitrocellulose and centralites may be ,carried out just as in the case of ethyl centralite, or if desired, the mixed centralites may be dissolved in the nitroglycerin and the solution sprayed on to'the water wet nitrocellulose, ac-

cording to the methods .well known in the art.

The usual processes of drying and gelatinizing the paste are then carried out, and it is in these that some of the advantages of the mixed centralites become easy to observe. The paste sheets are forme with great case on hot rolls, and final egelatiniza ion takes place veryreadily; The'operation of re-working faulty'sheets or cords is considerably facilitated owing to the flexible nature of the colloid produced when the mixed centralite'sareemployed. If it is desired to press 40 the gelatinized sheets into cord form, the great flexibility and plasticity of the. propellant are again in evidence. v

' Compositions which may be prepared according to the present invention consist in general of the following types:--

, Per cent Nitroglycerin or the like from to 15' Nitrocellulose from 40 to 80v Mixed centralites from a to 15 Other ingredients may be introduced according to ballistic requirements, orin order'toi b'ring about flashlessness or for anti-fouling purposes.,-.

Such in ri dients are; dinitrotcluene or trinitro-' the mixed centralites is unnecessary.

o! nitroglycerin, nitrocellulose toluene for ballistics; nitroguanidine for flashlessness: and tetrabutyl'stannane for anti-fouling. For many purposes, however, the use of ingredients other than nitrocellulose, nitroglycerin and For example, excellent results are given by the application of the present invention to propellant compositions of theiollowing proportions:

Parts by weight Nitroglycerin 41 Nitrocellulose- Mixed centralites 9 given represents proportions and gelatinizer, which have long been in use, with ethyl centralite being employed as gelatinizer-stabilizer. It is to be noted that the use of the mixed centralizes involves only a negligible change in the heat of combustion of the powder; also the stability of thepropellan't is not brought into question on account of the close similarity of the centralites in respect of stabilizing qualities. On the con- The example just trary, the increased ease of working produced by Y the use of the mixed centralites makes it possible to reduce the temperatures required for the rolling and pressing operations, and this reduction of temperature is a distinct benefit to the stability of the propellant.

Having now particularly described and ascertained the nature of my said invention, I declare that what I claim is:

1. The process of manufacturing gelatinized propellant explosives containing nitrocellulose and a liquid. nitric ester of a polyhydric aliphatic alcohol, which comprises gelatinizing the nitrocellulose with the nitric ester and a mixture of diethyl diphenyl urea and dimethyl diphenyl urea.

nitrocellulose, and a 2. The process of manufacturing 'gelatinized' propellant explosives containing nitrocellulose and a liquid nitric ester of a polyhydric aliphatic alcohol, which comprises gelatinizing the nitrocellulose with the nitric ester, and approximately 7'7 parts di-ethyl'diphenyl urea together with approximately 23 parts di-methyl diphenyl urea in each parts of the mixture. i;

3. A propellant explosive containing nitrocelluloseand a liquid nitric ester of a polyhydric aliphatic alcohol, which comprises a gelatinized mixture of diethyl diphenyl urea and dimethyl diphenyl urea.

4. K propellant explosive containing nitrocellulose andlra liquid nitric ester of a polyhydric aliphatic alcoholrwhichicompr ises a gelatinized nitrocellulose and a eutectic miiture oLd iethyl diphenyl urea and dimethyl diphenyl urea. T

5. The process of manufacturing gelatinized propellant explosives containing nitrocellulose and nitroglycerin, which comprises gelatinizing the nitrocellulose with the nitroglyceriuand a mixture of diethyhdiphenyl urea and dimethyl diphenyl urea. V

'6. The process of manufacturin gelatinized propellant explosives containing nitrocellulose and nitroglycerin, which comprises 'gelatini iing,

which comprises a gelatr 

